This invention pertains especially to applying a surface coating of a texturizing material over a drywall base substrate. It applies especially to applying the material in an economical and highly efficient operation. It is especially sensitive to applying a uniform textured coating that is adaptable in its ability to apply a variety of textures, and that provides a commercially acceptable texture.
A texture coating is used for several purposes. First, it is used as a base for applying paint. Second, it is used to cover imperfections in the drywall and its installation. Third, it is typically used to lend a surface texture to the wall being coated.
Coating material is conventionally applied to the drywall with a trowel or similar blade-type tool. After the material is applied, a texture is then imparted as by a dabbing motion, or by a sweeping motion of a patterned edge of, for example, the trowel.
Applying the coating to a vertical surface, or a ceiling, and having it stick to the surface, requires a significant amount of skill on the part of the person doing the work. Also, the work can be slow and tedious. The coating material, on the other hand, is relatively inexpensive. Thus, a significant portion of the cost of applying the coating is the cost of the labor involved in actually putting the material on the wall and creating a texture in it.
This invention also pertains to guns, and nozzles for projecting a material outwardly from the gun through the nozzle. The gun typically includes a means for receiving material from a supply source. This receiving means is conveniently a coupling which can receive a supply hose or other connector means. The gun also includes a valve for starting flow of the material through the gun, for stopping flow of the material, and for generally regulating the rate of flow of material through the gun. Material is projected from the gun typically through an orifice which is conventionally referred to as a nozzle. This invention pertains especially to improvements in design of the nozzle, and guns using the improved nozzles of the invention.
Conventionally, nozzles are known for spraying paint, lacquers, and the like-relatively low viscosity materials. Generally, a uniformly-dispersed surface coating is desired, and significant attention is usually directed toward obtaining a uniform coating surface. Such nozzles typically have a circular, elliptical, or slot-shaped opening. Typical of such nozzles are slit 9 in U.S. Pat. No. 2,737,415 and elliptical opening 82 in U.S. Pat. No. 3,930,619. Projection of conventional drywall coating material through these nozzles leads to totally unsatisfactory results. Satisfactory projection of this material through a nozzle is not believed to have previously been done. At ordinary pressures and using ordinary airless spray equipment, including ordinary nozzles, material which is capable of holding a texture cannot be projected with an acceptable degree of break-up of the material into the desired particles. Rather, the material comes out in streams and chunks.
The coating can be projected from an airless gun as in U.S. Pat. No. 3,930,619 by removing the nozzle and letting the material project as from the openings 28d and 48a, wherein a passage opens from the valve seat without passing through a patterning nozzle. While particles may be projected by such openings, a uniform pattern has not been obtainable thereby. An elongated path beyond the valve typically results in a stream, without an acceptable amount of break-up of the material into particles. A shorter path typically results in a non-uniform pattern.
It is not so necessary to completely atomize the coating material as it is to project it in discrete particles which will adhere to the drywall in esentially the projected pattern. The particles should range in size up to no more than about 2 centimeters diameter, preferably about 1 cm., depending on the preference of any one particular customer. Particle size is measured as the splattered particle on the drywall substrate. The pattern should include a range of particles down to about 0.1 cm, with an overall background coating.
It is not believed that any means has previously been provided for applying drywall coating compound with airless spray equipment, where the coating compound is projected as particles which provide a textured surface. The inventor herein has conceived that it may be possible to project the desired particle sizes by use of air-atomizing spray equipment. However, that equipment is several times more costly than airless equipment. It is more bulky, and thus less adaptable to being moved about the interior of a building to do the job. Further, the greater bulk of the air atomizing equipment requires more trucking capability to move it to and from the job site. Thus is the airless operation highly desired if a satisfactory spray pattern can be developed.
For use in applying a coating compound over drywall, it would be desirable to be able to control the relative size of the particles of material projected from the nozzle. In some cases it is desirable that all the particles be relatively fine in order to apply a fine textured, and uniform coating. In other circumstances, it is more desirable to have a rougher textured coating, such that the particle size range includes some larger particles. Thus the nozzle should incorporate some means for adjusting the size of the particle which is being projected from the gun.
It is an object of this invention to provide a novel gun, and novel means, for projecting material therefrom.
It is a further object of the invention to provide a novel nozzle which is capable of projecting material in a substantially controllable pattern.
It is yet another object to provide the capability, in the nozzle and the gun, of adjusting the range of the sizes of the particles projected from the gun.